OPTICAL SCANNING DEVICE AND IMAGE FORMING APPARATUS USING THE SAME

摘要

An optical scanning device includes a rotary polygonal mirror for scanningly deflecting light beams emitted from a light source device having light emitting members disposed spaced apart from each other in a main-scan direction, an input optical system by which, in a sub-scan section, light beams are incident on a deflecting surface of the rotary polygonal mirror in an oblique direction with respect to a normal to the deflecting surface, and an imaging optical system by which the light beams scanningly deflected by the rotary polygonal mirror are imaged on a surface to be scanned, wherein, when a maximum pivot angle of said rotary polygonal mirror is theta_max [deg], the angle defined in the main-scan section between optical axes of the input optical system and the imaging optical system is 2ø [deg], the focal length of a converting optical element in the main-scan section is f_col [mm], the spacing between two light emitting members most spaced apart from each other in the main-scan direction is a [mm], the largest oblique incidence angle in the sub-scan section of the light beams incident on the deflecting surface is alpha [deg], the imaging magnification of the imaging optical system in the sub-scan section is betas, the inscribed-circle radius of the rotary polygonal mirror is denoted by R [mm], and the resolution of an image in the sub-scan direction is denoted by DPI [dot/inch], a conditional expression $\frac{\tan {\mathrm{theta}}_{\max }}{\cos \mathrm{phi}}x\frac{a}{\mathrm{fcol}}xRx\mathrm{beta}sx\tan \mathrm{alpha}x\frac{DPI}{25.4}<=0.05$ is satisfied.